i belive age of wood used is more important - natural growth lumber that used to be available is much better quality than the farmed wood that is readily available today. I belive that makes more difference than the aging of the wood

however as wood ages, on a good quality insturment the resins in the wood get harder and the resonance changes, in most cases for the better, but cheap guitars can deteriorate because of warping or delamination of body peices. I have heard plenty of guitars that sounded better as they aged as well as others that sounded worse.

also pickups age, they loose strength and their crispness - this is good for hard rock, blues, jazz or cleans but maybe not for metal - i personally like aged pickups

In general the biggest factors in the sound of your instrument are in my opinion in this order ( excluding amps cords and effects )

- your fingers

- craftsmanship

-quality of woods used

-quality of electronics used

-pickup selection appropriate for the woods and bridge type and for your playing style / sound you are trying to achieve

- also the type of material your pick is made from (if you use one) can make a surprisingly large difference in your sound. tortex, polyethelene, celluloid, nylon, acetal, metal, wood all sound very different. I use tortex most of the time for a bright sound, celluloid if I want to melow my tone out a bit, and acetal ocassionally if I want an even darker sound.

My Carvin was built around 1985, I acquired it in 2008 and I believe its been sounding better and better with time. Might just be that I continue to grow fonder of her, but who knows? My stealth is much the same, although she & I have a bit of a love/hate relationship from time to time. Some days she just sounds thin & brittle and some days the tone is godly perfect.

i think the pickup plays important roles as well. I own a 1996 Washburn Dime 333. The original bridge W2 pickup kinda lost its treble/high a bit somehow . So i took off the old pickup and switch to a new Bill Lawrence L500XL. The Outcome were awesome.

I don't consider myself some epic long time player. Most of my guitars don't last longer than 3 or 4 years (which is why I don't spend big money on them), but the ones that have went the distance just felt broke-in to me. They're easier to play, feel better, and sound better. It may be because I finally got used to the settings and become accustomed to them. Even if I like a guitar it takes about a year for me to warm up to it. But I think that just wearing a string across a fret in your particular style causes it to get in the groove over time and will naturally get in sync.